Pulverulent-fuel furnace



C.DUQUENNE PULVERULENT FUEL FURNACE Filed Oct. l0, 1925 2 Sheets-Sheet 2: -M Lue; f f r AU 2 Sheets-Sheet 2 C. DUQUENN PULVERULENT FUEL FURNACE Filed OCT.. l0, 1925 721 ven Tof wlilllallll 1 -NHJ Dec. 4, N28.

Patented Bec. 4, i928.

unirse. snare-s Y innate? 'CAMILLE DUQUENNE, 0F PARIS, FRANCE.

riJLvERULENT-FUEL summon.

Application filed October 10, 1925, Serial No. 61,719, and in France October 27, 1924.

One of theprincipal difficulties encountered 1n the operation of pulverulent fuel furnaces is due to the agglomeration and caking of deredfuel which are disposed for instance at 10 1n the front .portion 1. The side walls 2 are cooled by an airv circulation to which the ashes upon the hearth 0f the combustion \a.ir is supplied by the adjustable air inlet gates chamber which ashes are melted under the iniuence of the high temperature to which they are subjected. To obviate this caking of the ashes it has already been proposed to use a grate or screen of stationary tubes, kcooled by water or compressed a/ir, or a grate of hollow air cooled bars or pipes each made of a single piece. It is proposed to arrange this grate between the combustion chamber and the ash pit, so that the radiation of the heat from the combustion chamber upon the ash pit is entirely or partially eliminated. These arrangements however are attended with serious drawbacks as the deterioration or damage of one tube, due to expansion or any other` cause, may result in an interruption of the service, and the failure of such a tube is often the cause of accidents.

The present invention has for its object to eliminate the calling of the ashes upon the hearth of the combustion chamber by means of a particular arrangement of such cooled tubes or conduits whereby the above mentioned drawbacks are eliminated.

The invention essentially consists in installing between the combustion chamber and hearth a plurality of stationary juxtaposed air conduits forming an air screen, and by the provision of means whereby the cooling air may circulate in said conduits, certain special constructive arrangements being provided in said air conduits whereby their supports are protected by refractory covering and their constitutive elements may be easily replaced.

The appended drawing shows by way of example an embodiment of the invention, as applied to a multitubular steam boiler. Fig. 1 is a verticallengthwise section and Fig. 2 a vertical cross section on the line II--H of Fig. 1. Figs. 3 and 4 show the arrangement of an air conduit on a larger scale Fig. 3 is a lengthwise section of a part of said conduit and Fig. 1 a cross section.

1 is the front wall and 2 the side walls, 3 the fire bridge, 4 the arch, 5 the hearth. The boiler apparatus is diagrammatically represented by its upper drum 6, the lower drum 7, the vaporizing tubes 8 and the return tubes 9, but it is obvious that the boiler may be of any desired type and construction. The combustion takes place in the combustion chamber C by the use of burners employing pow- 13 disposed at the upper part of the said chamber and supplying air through the flues 12 and 12 to the middle and the lower part of the said chamber by means of the ports 11.

According to my said invention, I provide at a suitable distance above the hearth a plurality of air conduits A which in the example are juxtaposed in the parallel position and proceed from the front wall which is provided with an air intake for each conduit, to the fire bridge 3 at which point the air which is heated by its circulation through the said conduits will now pass upwardly through the fiues 15, thence flowing by way of the ports 16 tothe combustion chamber, the circulation being ensured in an adjustable manner through the doors 14 by the vacuum prevailing in the furnace, so that the fire bridge will be cooled and the air which is preliminarily heated can be utilized for combustion purposes while at the same time protecting the upper part of the re bridge, around which it circulates, from the direct contact with the gas in combustion.

In the present example, the conduits A are constructed as follows: Upon the I beams 17, serving as supports between the front wall and the iire bridge, are disposed the cast iron tubes 18 which are connected together by suitable joints andare employ-ed as air conduits; said tubes are protected by refractory covering members 19 and 20. l provide a simple arrangement comprising cast iron tubes 18 provided at the lower part with the hooked lugs 18. The members 19 and E20 have such a shape that the lateral members 20 rest at the bottom upon the hookedmembers 18 and are secured at the upper part by the edges of the upper members 19. The said members can thus be removed and replaced in a simple and rapid manner. Since the cast iron conduits are protected by their refractory coverings and are cooled by the air circulation, they will last for a long time, and' on the other hand, the I irons which support the said cast iron tubes will be in Contact therewith only at certain points, and are in contact at their entire surface with the circulating air, so that they will alsolast for a long time. j

The cooling grate which is thus formed by the said lair conduits will suffice to attain the desiredend, which is to constitute a screen los capable of arresting or attenuating the radia.

tion from the combustion region upon the hearth and of preventing the agglomeration of the ash. Should one of the said conduits be damaged, this will occasion no accident nor any stoppage of the boiler or furnace, and when the plant operates in these conditions, at least during a certain time, this will cause no serious inconvenience.

Obviously, the air conduits, which are in practice juxtaposed in parallel position with suitable spacing, may be otherwise disposed, and the air may be circulated by other means or by forced circulation; the construction and the support of the said conduits may be modified, as well as the several dispositions and the details of construction, without departing from the principle of the invention.

Claims:

1. In a furnace using pulverulent fuel including adevice forming an air grate placed between the combustion chamber and the ash pit, a plurality of inner air circulating conduits, refractory elements covering said conduits and carried thereby, each of said conduits comprising a number of interlitting iron sections, and a metallic beam lodged Within and supporting each of said conduits, Said beam being arranged in such a manner as to be bathed upon its entire surface except the supporting surface by the air circulating within said conduit.

2. In a furnace using pulverulent fuel. including a device forming an air grate placed between the combustion chamber and the ash pit, a plurality of inner air circulating conduits, refractory elements covering said conduits and carried thereby, each ofA said conduits comprising a number of intertting iron sections, a metallic beam lodged within and supporting each of said conduits, said beam being arranged in such a manner as to be bathed upon its entire surface except the supporting surface by the air circulating within said conduit, a re bridge at the rear of the furnace and provided with lues, the said conduits extending from the front of the furnace into the flues of the re bridge whereby the upper part of the fire bridge is cooled while the heat 'contained in the heated air is recuperated;

3. In a furnace using pulverulent fuel in- A duits coinprisinor a number of interfitting iron sections, a metallic beam lodged within and supporting each of said conduits, said beam being arranged in such a manner as to be bathed upon its entire surface except the supp-orting surface by the air circulating within said conduit, a fire bridgeat the rear of the furnace and provided with flues, the said conduits extending from the front of the furnace into the said iues whereby the upper part of the fire bridge is cooled while the heat contained in the heated air is recuperated, and adjustable inlet means in said conduits to provide access to the said metallic beams.

4. In a furnace usingpulverulent fuel includnga device forming an air grate placed between the combustion chamber and the ash pit, a plurality of inner air circulating conduits, each comprising a number of intertting iron sections, flanges provided upon the lower part of said conduits, refractory elements covering said conduits and carried thereby, said refractory elements comprising two lateral parts and a top par-t, the lateral parts being held in place bythe' top part and being supported at their lower edges by said conduit flanges, a metallic beam lodged within and supporting each of said conduits, said beam being arranged in such a manner as to be bathed upon its entire surface except the supporting surface by the air circulating within said conduit, a fire bridge at the rear of the furnace and provided with nues, the conduits extending from the front of the furnace into the flues whereby the upper p-art of the fire bridge is cooled while the heatacontained in the heated air is recuperated, and adjustable inlet means in said conduits to provide access to said metallic beams.

CAMILLE DUQUENNE. 

